Digital cross-connect systems are an integral part of today's modern telecommunications transport network. They are increasingly used by all service providers including exchange carriers, long distance carriers, and competitive by-pass carriers. Significant technology advancements have allowed digital cross-connect systems to evolve from narrowband grooming and test applications to cross-connection of larger network signals in wideband and broadband frequency domains.
Conventional digital cross-connect systems have largely been based on a single core architecture approach where all cross-connections are made through a single switching node or matrix. However, most transport network architectures are based on a layered signal structure where one layer must be completely exposed or processed before accessing the next layer. To completely handle layered signal structure network architectures, digital cross-connect systems capable of handling different feature requirements must be connected in series.
For multiple digital cross-connect systems connected in series, a broadband system is first used to terminate high speed optical and electrical signals in order to path terminate and groom lower speed broadband signals. The broadband system also supports performance monitoring and test access functions. A payload containing the broadband signals is then connected to a wideband system to support similar functions in obtaining wideband signals. The wideband signals are then terminated by a narrowband system. For a hub office, the procedure is done in reverse order in order for signals to leave the office.
As new services, new capabilities, and new network transport signals that increase network complexity develop and evolve, a higher emphasis is placed on test access functions to improve network survivability and service quality through quick fault isolation and reduce outage duration. However, in conventional cross-connect systems connected in series, once a signal is terminated to extract embedded signals, access monitoring and test of the terminated signal is lost.
A series of single digital cross-connect systems cannot provide complete test access to signals carried over the network. Failure to provide complete performance monitoring, test access, path termination, and grooming functions at all network levels can significantly impact network survivability and office flexibility.
From the foregoing, we have recognized that a need has arisen for a digital cross-connect system that overcomes the reliability problems of conventional digital cross-connect systems. We have conceived that there is a utility for a digital cross-connect system that can perform complete test access and monitoring of all signals in a layered signal structure. Further, it would be advantageous to have a single cross-connect system that can process all signals embedded within a multi-layer signal structure.